Conventionally, it is possible to easily carry various information by using a memory card such as an SD card or the like. By connecting the memory card to an electronic device, it is possible to import various information stored in the memory card into the electronic device to perform processing in the electronic device. In addition, various information can be written into the memory card.
In recent years, with an increase in the capacity of the memory card, personal information and secret information are increasingly stored in the memory card. In addition, with enhanced awareness of security of a user using the memory card, there exists a memory card requiring an input of a password in order to refer to and update information in the memory card, and newly store information in the memory card.
For example, there is adopted a system in which the information in the memory card can be freely accessed when the password is not set in the memory card, but the memory card is brought into a locked state unless correct password information is transmitted to the memory card so that the information in the memory card can not be accessed when the password is set in the memory card. Thus, when the memory card is in the locked state, by transmitting the correct password information to the memory card to bring the memory card into an unlocked state, the information in the memory card can be accessed.
In the memory card requiring the input of the password, when the password is forgotten, it becomes impossible to read stored data protected by the password, update a storage area protected by the password, and newly write data in the storage area. In addition, also in the electronic device such as a PC or the like to which the memory card is connected, it becomes impossible to use (read and write) the memory card.
Consequently, there is known an information device in which a sub-password is provided in addition to an actual password, and the password is cleared or redisplayed by using the sub-password when the actual password is forgotten (see, e.g., Patent Document 1).
In addition, there is known a password control method in which a password is generated by a system and stored in a storage medium for a user to prevent the password from being forgotten by the user, allow use of a complicated password, and improve safety of the system (see, e.g., Patent Document 2).
Patent Document 1: JP-2004-133670A
Patent Document 2: JP-3-192456A